[PATCH v2 4/5] target/ppc/power8-pmu-insn-cnt: add pmu_check_overflow()

[Daniel Henrique Barboza <danielhb413@gmail.com>]

pmu_check_overflow() will verify for overflow in the PMC1-5 counters,
firing a performance monitor alert if an overflow happened with the
proper MMCR0 bits set.

The alert is fired by using helper_pmu_overflow().

Signed-off-by: Daniel Henrique Barboza <danielhb413@gmail.com>
---
 target/ppc/helper.h                  |  1 +
 target/ppc/power8-pmu-insn-cnt.c.inc | 76 ++++++++++++++++++++++++++++
 target/ppc/power8-pmu.c              |  8 +++
 3 files changed, 85 insertions(+)

diff --git a/target/ppc/helper.h b/target/ppc/helper.h
index fb6cac38b4..4d8193caab 100644
--- a/target/ppc/helper.h
+++ b/target/ppc/helper.h
@@ -26,6 +26,7 @@ DEF_HELPER_2(store_mmcr1, void, env, tl)
 DEF_HELPER_3(store_pmc, void, env, i32, i64)
 DEF_HELPER_2(read_pmc, tl, env, i32)
 DEF_HELPER_2(insns_inc, void, env, i32)
+DEF_HELPER_1(pmu_overflow, void, env)
 #endif
 DEF_HELPER_1(check_tlb_flush_local, void, env)
 DEF_HELPER_1(check_tlb_flush_global, void, env)
diff --git a/target/ppc/power8-pmu-insn-cnt.c.inc b/target/ppc/power8-pmu-insn-cnt.c.inc
index a5a0d42e71..6e0e4e1270 100644
--- a/target/ppc/power8-pmu-insn-cnt.c.inc
+++ b/target/ppc/power8-pmu-insn-cnt.c.inc
@@ -18,6 +18,8 @@
 #define MMCR1_PMC4_INS_CNT        0x00000002
 #define MMCR1_PMC4_INS_LATCH_CNT  0x000000FA
 
+#define PMC_COUNTER_NEGATIVE_VAL  0x80000000UL
+
 /*
  * This function increments a SPR 'spr' by 'inc_val' if a given
  * register 'reg' has a bitmask 'mask' set (cond = TCG_COND_EQ) or
@@ -47,6 +49,78 @@ static void inc_spr_if_cond(int reg, uint64_t mask, TCGCond cond,
     tcg_temp_free(t0);
     tcg_temp_free(t1);
 }
+
+/*
+ * Check for overflow of PMC1-PMC5 counters and call the overflow
+ * helper in case any counter has overflown.
+ */
+static void pmu_check_overflow(DisasContext *ctx)
+{
+    TCGv t0, t1, t_pmc1, t_pmc;
+    TCGLabel *l_pmc_overflow;
+    TCGLabel *l_skip_pmc1_overflow;
+    TCGLabel *l_skip_overflow;
+    int i;
+
+    /*
+     * Check if we have overflow bits set and fire an overflow
+     * event if necessary. Skip directly to 'l_pmc_overflow'
+     * right after finding the first overflow.
+     */
+    l_pmc_overflow = gen_new_label();
+    l_skip_pmc1_overflow = gen_new_label();
+
+    t0 = tcg_temp_new();
+    gen_load_spr(t0, SPR_POWER_MMCR0);
+    tcg_gen_andi_tl(t0, t0, MMCR0_PMC1CE);
+    tcg_gen_brcondi_tl(TCG_COND_NE, t0, MMCR0_PMC1CE, l_skip_pmc1_overflow);
+
+    t_pmc1 = tcg_temp_new();
+    gen_load_spr(t_pmc1, SPR_POWER_PMC1);
+    tcg_gen_brcondi_tl(TCG_COND_GE, t_pmc1, PMC_COUNTER_NEGATIVE_VAL,
+                       l_pmc_overflow);
+
+    gen_set_label(l_skip_pmc1_overflow);
+
+    l_skip_overflow = gen_new_label();
+
+    /*
+     * At this point we're sure PMC1 didn't overflow. If MMCR0_PMCjCE
+     * isn't set we can skip everything since PMC2-5 overflow is
+     * disabled.
+     */
+    t1 = tcg_temp_new();
+    gen_load_spr(t1, SPR_POWER_MMCR0);
+    tcg_gen_andi_tl(t1, t1, MMCR0_PMCjCE);
+    tcg_gen_brcondi_tl(TCG_COND_NE, t1, MMCR0_PMCjCE, l_skip_overflow);
+
+    for (i = SPR_POWER_PMC2; i < SPR_POWER_PMC6; i++) {
+        t_pmc = tcg_temp_new();
+        gen_load_spr(t_pmc, i);
+        tcg_gen_brcondi_tl(TCG_COND_GE, t_pmc, PMC_COUNTER_NEGATIVE_VAL,
+                           l_pmc_overflow);
+        tcg_temp_free(t_pmc);
+    }
+
+    tcg_gen_br(l_skip_overflow);
+
+    gen_set_label(l_pmc_overflow);
+
+    /*
+     * The PMU overflow helper manipulates the internal PMU timer.
+     * In that case, if the guest is running with icount and we do not
+     * handle it beforehand, the helper can trigger a 'bad icount
+     * read'.
+     */
+    gen_icount_io_start(ctx);
+    gen_helper_pmu_overflow(cpu_env);
+
+    gen_set_label(l_skip_overflow);
+
+    tcg_temp_free(t0);
+    tcg_temp_free(t1);
+    tcg_temp_free(t_pmc1);
+}
 #endif /* #if defined(TARGET_PPC64) && !defined(CONFIG_USER_ONLY) */
 
 #if defined(TARGET_PPC64)
@@ -115,6 +189,8 @@ static void pmu_count_insns(DisasContext *ctx)
 
     gen_set_label(l_skip_pmc14);
 
+    pmu_check_overflow(ctx);
+
     tcg_temp_free(t_mmcr0);
     tcg_temp_free(t_mmcr1);
     tcg_temp_free(t_ctrl);
diff --git a/target/ppc/power8-pmu.c b/target/ppc/power8-pmu.c
index 08d1902cd5..6696c9b3ae 100644
--- a/target/ppc/power8-pmu.c
+++ b/target/ppc/power8-pmu.c
@@ -323,6 +323,14 @@ void helper_insns_inc(CPUPPCState *env, uint32_t num_insns)
     }
 }
 
+/* Helper to fire a PMC interrupt from TCG code */
+void helper_pmu_overflow(CPUPPCState *env)
+{
+    PowerPCCPU *cpu = env_archcpu(env);
+
+    fire_PMC_interrupt(cpu);
+}
+
 static void cpu_ppc_pmu_timer_cb(void *opaque)
 {
     PowerPCCPU *cpu = opaque;
-- 
2.33.1